Metadown

tl;dr… This gem gives you a custom markdown parser that allows you to prefix the
markdown itself with YAML metadata.

Sometimes, just having plain markdown isn’t good enough. Say you’re writing
a blog post, and you want to include some information about the post itself,
such as the date and time it was posted. Keeping it in a separate file seems
like a bad idea, but Markdown doesn’t have any good way of doing this.